Antenna and coupler system



Jan. 4, l938.- R. B. IYDOME i 2,104,610

ANTENNA AND COUI LER SYSTEM.

Filed Dec. 24, 1934 FREQUENCY RAD/0 1940/0 H500 v/?. RECE/ l/E/P.

Invfltof? RobePtBDm-ne,

His Attorney.

Patented Jan. 4, 1938 UNITED STATES ANTENNA AND COUPLER SYSTEM Robert B. Dome, Bridgeport, Conm, assignor to General Electric Company, a corporation of New York 1 Application December 24, 1934, Serial Noe 7 58 9 Claims.

My invention relates to antenna ,and antenna coupling systems for radio .;receiver and transmitter apparatus, and its special object is to provide an antenna and coupler system such that 5 transfer of radiant energy may be effected with improved efliciency byithe antenna and coupler system over a wide range of Wave bands.

The problem of providing a satisfactory antenna for use in conjunction, for example, with all-wave radio receivers to cover a'wide 'frequency band is 'difiicult ofsolution where it is desiredto have no separate antenna tuning equipment, ,or antenna adjustment on the-receiver. p

Desirable characteristics of an antenna for such use include the following? The antenna should not require a separate adjustment on the receiver, or at an external unit; the signal levelprovided by'the'antenna should beuniformover the desired range of frequency; the signal level provided by the antenna should be as high as possible; the antenna should'be designed to be free of pickup of local noise currents; the antenna'shouldnot be limited-in its application by'restricting either the lead-in length, the height, or the antenna length to a rigid figure; the antenna'shouldbe simple in construction. V

A difiiculty in solvingthe problems involved in providing a suitable antenna :for "all-wave radio apparatus resides inthe fact that the impedance of an antenna ordinarilyvaries over wide limits periodically with "frequency in a non-linear and practically discontinuous manner. Therefore simple tuned circuits which are fixed in tuning cannot satisfactorily tune the antenna over the entire-range'of wave bands. The solution of this latter problem would be to provide if possible an antenna which is not characterized by wide variations in impedance over'the frequency range. This result could be obtained by making the 'antenna system short physically'so that thelength of one feeder wire out to the end of the'antenna wire would always be less than half a wave length. Such an arrangement,however, would call for'an "antenna system so short, as required for use with the highest frequency band, that its efliciency over the lower frequency'bandswould-be-quite low. My present invention provides 'for'the use of an antenna-system which is longer physically and therefore much more eflicient in the low frequency bands than the short antenna system above noted.

In order to provide an antenna which, in connection with means for coupling-the antenna to a radio apparatus 'circuit' such-as an input circuit of a radio receiver, has the (desirablecharacteristics hereinabove set forth, I have utilized a nonuniform transmission line as a feeder for, or a constituent part of the antennasystem. Such a non-uniform transmission line may be, ior'example, a line which is characterized by an ever increasing elementary inductance and a fixed elementarycapacity. The effect produced'by a transmission line of this character can beestimated and approximately solved by dividing up the line into small finite sections, eachsection a u'nl'formline. This means that the-frequency A range overwhich the antenna system 'including such 'a non-uniform transmission line maybe 'usedbefore the half-wave resonance point of'the reactance curveis reached is considerably extended, the system therefore covering efficiently a 7 'wide range of wave bands.

The antenna system in accordance with my invention comprising the nonuniform transmission line may be considered as of the single dou- 'blet type,two oppositely extending conductors being continuations of, or connected to, or merging into apair of converging conductors The converging'conductoraat their inner ends, maybe continued by, or connected to, a pair of conductors arranged closely adjacentthrou ghout' their 7 length, .for example a twisted pair of conductors. 35

;In order thatla highly eflicient transfer of energy 'may be obtained'in all directions perpendicular to, or broadsideto the antenna conductors,the

rate at which the'transmission line conductors 1 diverge from the apexoi? the openingis preferably relatively rapid, this rate of..;divergence being such that energy transfer in the above-noted directions perpendicular to, or broadside to the conductors is substantially as great as in the direction ofthe axis; The antenna in accordance with .my invention is therei ore substantially bi"- directional. v

*Preferably the antenna comprising the non uniform transmission line is'arranged as a verti-' cal antenna, the axis, or line bisecting the open-f ing tamed by the diverging pair of conductors being "substantially vertical. However, the antenna under certain conditions may be arranged asa' horizontal antenna, the axis or line bisecting means for so connecting the antenna to a radio device such as a receiver that the antenna operates over the high frequency range of wave bands as a doublet including a noise-reducing system, substantially all of the pick-up of energybeing due to the antenna proper and little or from being due to the lead-in or twisted pair; and that the entire antenna system including the lead-in operates as a simple antenna over the low frequency or broadcasting band and on other adjacent relatively low frequency bands if desired. It is a further feature of my invention that in its preferred form the coupling means is so arranged that the change of the antenna system from doublet,

noise-reducing operation on the high frequency bands to simple antenna operation on the relatively low frequency bands is effected automatically.

My invention will be better understood from the following description when considered in connection with the accompanying drawing and its scope will be pointed out in the appended claims.

Referring to the drawing, Fig. 1 is a diagrammatic representation of a radio apparatus embodying my invention; Fig. 2 is a diagrammatic representation of one form of a coupling means between an antenna. and a radio device; Fig. 3 is a diagrammatic representation of a coupling means including automatic means for changing from doublet operation to simple antenna operation; and Fig. ,4 represents curves indicating graphically the reactance at varying frequency for uniform and non-uniform transmission lines respectively.

In Fig. 1 the numeral l0 indicates a radio device which in the present embodiment of the invention is represented as a portion of a radio receiver ofthe all-wave type comprising a plurality of input circuits as H, l b-which may be connected, in the usual manner as required for the reception of different wave bands, to input terminals l3, l4 through a suitable switch means l5. Since the radio receiver or similar radio device per se forms no part of the present invention it will not be described further herein.

In order to supply radio signals to the radio receiver device Ill an antenna system designated generally by the numeral I6 is provided, adapted to be coupled to the selected one of the input circuits H, |2by a coupling means, designated generally by the numeral II, which will be more fully described hereinafter. The antenna system I6 comprises open end portions l8, H! extending or'diverging in opposite directions and gradually converging at their inner ends into. a, non-uniform transmission line. The wire portions l8, 19 -may be merely divergent as shown for example in Fig. 1, or they may be in line, pointing 180 away from each other in substantially the same position as usual doublet antenna wires. The non-uniform transmission line portion of the antenna systemfurther includes the pair of conductor portions 20, 2| diverging from the apex point 22 of the opening 23 formed therebetween at a relatively rapid rate and 0on tinuing to flare out to join the portions l8, I9. The portions 20, 2| may diverge smoothly as shown, or the divergence may be accomplished in a series of straight steps thereby lessening the number of guys or stays required to maintain the antenna in the desired form. The non-uniform transmission line portion of the antenna merges into a lead-in 24 constituted by a pair of conductors 25, 26 which are closely adjacent throughout their length and are preferably arranged, as shown in Fig. 1, as a twisted pair.

:Referring to the coupling means hereinbefore mentioned for'connecting the antenna, system to the radio device, the form of this couplingmeans shown in Fig. 2 and designated generally by the numeral 21 comprises a coupling coil 28, a mid-tap 29 which may be connected to one input terminal, as the grounded tenninal 14 of the radio device, or to ground, one extremity-30 of coil 28 being connected to another terminal |3 of the radio device. The lead-in conductors '25} 26 are connected respectively to the ends' of coil '28. In order to prevent pickup at high frequencies by the lead-in 24 the two halves'3l, 32 of coil 28'a're closely coupled. The

m'id-tapped coil 28 of Fig. 2 is, however, preferably replaced by a coil 34 arranged, as shown in Figs. 1 and 3, as a step-up autotransformer having two taps 35 and 36, tap 36 being a mid-tap between tap 35 and one end 31 of coil 34. The lead-in conductors 25, 26 are connected respectively to tap 35 and coil end 31. The mid-tap 36'may be placed in electrical connection with one input terminal, as the grounded terminal I4 of the radio device, or to ground, and the other other input terminal l3 of the radio device.

In order to change from doublet operation to simple antenna operation the tap 29 of Fig. 2, or the tap 36 of Figs. 1 and 3, may be simply disextremity 38 of coil 34 may be connected to anconnected from ground thi manual shifti from doublet operation to simple antenna operation beingfacilitated if desired by means of a switch, such as switch 39 shown in Figs. 1 and 2 in the lead between tap 29 or 36 and radio receiver terminal l4, and ground.

- l The shift between doublet and simple antenna operation is, however, preferably accomplished, in accordance with my invention, by the means illustrated inconnection with Fig. 3; In order to avoid the necessity of manual operation of a switch or other means, and to eliminate such switch or other mechanically operating means for shifting between doublet and simple antenna operation, I provide a capacitance means, illustrated as a condenser 40, providing such capacity that the shift between doublet and simple antenna operation is accomplished automatically.

Referring, to the operation of the antenna system 16 illustrated in Fig. 1 it will be understood that since the antenna system, from its outer, wide open, flared portion, gradually converges into a transmission line, the system has thecharacteristics of a non-uniform transmission line, and the surge impedance of the system therefore diminishes as the line approaches the radio receiver In. For example, the outer portion of the antenna proper may have a surge impedance of 500 .ohms, but that part of the an.- tenna system finally connected to the radio receiver may have a surge impedance of but ohms. The tapered transmission line therefore operates somewhat as a transformer tending to lower the relatively high impedances, out on the antenna, to moderate values of impedance which wave band. The curve .43, however, illustratesthe reactance curve for a non-uniformtransrnissio line, such as hereinbeiore described, of the same length phys'icallyas the uniform line, Whose re.- actance curve is illustrated as curve 4|. For the given frequency range it willbe seen as indicated by curve 43 that, in the case of the non-uniform transmission line, a far greater frequency range is passed over before a half wave, resonance point, 44 of curve 143, is reached than m thecase, of the uniform line. The incorporation in the antenna system E6 of the non-uniform transmission line therefore ensures, for an antenna which is physically of the single doublet type, efficient pick-up or radio signals over' relatively broad ranges of high frequency wave bands.

Since the rate of divergence of the pairs of conductors 20, 2! from the ape 2 of the opening 23 between these, flaring conductors, which are continued to form the portions liland I9, is relatively "rapid, a highly eflicient transfer of radio energyby the antenna occurs in all direc': tions substantially perpendicular to the line formed by the finally expanded antenna wires. The antenna system I6 is therefore essentially Iii-directional.

The antenna structure I6 is preferably mounted as a vertical antenna asshown in Fig.1. It is to be understood, however, thatunder some conditions, as in case the antenna is located on the roof of a building, the antenna system may be mounted if desired with the axis substantially horizontal. The opp'ositely'extending por tions l8 and is are shown in 'Fig. 'lfas being -of the same order of length as the distance between the points 45 and 4 which mark'approxirnately the points of merging of the endportions i8, -Ill into converging portions 2!], 2|. However, to suit the length of span to a given location the spread of the antenna may be reduced, with some corresponding loss of pick-up, by reducing "the length of the portions l8, I9. I have found, further, that in order to make the antenna'systern less unwieldy in erection, the distance between the points 46 and 41 may be about one-half the length of the oppositely ektending portion 18 or I9. The. distance between the points 46 and 41 may be of the same order of magnitude as the distance between the apex point 22 and line joining the points 46, 41. The length of the leadin 24 is not critical, but a reasonably short leadin should be used since the use of long lengths of uniform transmission line, such as the lead-in 24, near the radio receiver brings the half-way point down in frequency.

In operation of the coupling means which is combined with the antenna system Hi to form an antenna unit capable of attachment to existing radio receivers, during operation of the apparatus on high frequency wave bandsany currents picked up by the lead-in. conductors will enter the coil 28 of Fig. 2 for example, or the coil 48 of auto transformer coil 340i Fig. 1, from op.

- 39 w ch is closed this purpose.

asket-90 .1 19? and-w l th nce pa hrou h the n i E a 2 9 1, the mid-tap 1291s 3t beingconnected ie tt e s 9 bs-ant n a s t m '6 wi opera in he us a ma a a oub e ntenna, any radio signals picked up by this doublet portion enteringthe coil 28 of Fig. 2, or the coil '41} of 1, at one end oi. these coils and leaving by the other end, thereby setting up a voltage from 30to 29 of coil 28, or from 35 to 36 ofcoil 48, duetothe IX drop acrossone-hali of either of these. coils. Since in Fig.2 the half of; coil 28,. between 30 and 29 is connected to the. input terminals of the radio receiver, the radio signals picked up by that part Q h n nna t m th r an th ead in 24 will be impressed on the. radio receiver. Likewise inFig. 1, since the high tension point '38 n m d-ta 3' of c 34 a nnect d t9 e terminals ,of the radio receiver, theradio signals picked upby the doublet portionof the antenna are impressed on the receiver, the portion of coil 34 between.3 8 and 35 serving to step up the voltage set up between points 35 and 36.

For. operation inth broadcast band,or in the latter band and any other adjacent relatively low frequency band, the lead-in and the doublet portion, or antenna proper, are both utilized as piclg up means for radio signal currents. For this purpose mid-tap-ZS, of .coil 28 of Fig. 2 or mid-tap 3%} of coil 34 of Fig. 1 may be disconnected from ground as by the opening of switch 39. The entire antenna system l6, includingthe lead-in portion 24 and the other, or doublet por tion, then operates :to impress signal voltage across the input terminals l3, I4 of the radio receiver,

Reierring particularly to the operation of the automatic means'fer shifting between doublet andwsim le an nna pe at a u r d. Fig. 3, the capacitance means, shown as the con dens r 0.11 r s ch c cit that t hi radio f reguencies, for example 6 megacycles and higher, the-reactance of the capacitance between the midetap point 36 of coil 48 and ground is so low thatthis mid-tap point is effectively grounded; The antenna system l5 then operates as herein'-. beforedescribed in connection with the operation, on high frequencies and with switch 39 closed, of the system shown in Fig. 1, any manmade noise signals picked up by the lead-in portion 274 being cancelledout. The remainder, or doublet portion of the antenna system operates to impress desired radio signals on the input of the radio receiver. At lower frequencies, however,- for example onthe broadcast band and also on other relatively 'long wave bands adjacent the. broadcast band, the reactance of the capacitance means represented by the con-v It will be seen from the foregoing description of my invention that I have provided an antenna system which may take the form of an antenna unit or kit comprising an antenna preferably incorporating a non-uniform transmission line together with a coupling means, the entire system being adapted to be connected if desired as a unit to the input terminals or input circuits of existing radio receivers, the unit being of such character that highlyeificient pick-up of radio signals over wide ranges of high frequency wave bands and desired ranges of low frequency wave bands is insured, the change from doublet operation on high frequencies to simple antenna operation on low frequencies being effected automatically and without complication or added expense.

The antenna in accordance with my invention has been illustrated and described herein mainly in connection with radio receivers. It will be understood, however, that the antenna of the non-uniform transmission line type herein de scribed is applicable to radio transmitters, particularly to radio transmitter use wherein an antenna of good efliciency is required to transmit signals over a relatively wide frequency band without, during operation over any point of this band, reaching the half-wave resonant point.

My invention has been described herein in particular embodiments for purposes of illustration. It is to be understood, however, that the invention is susceptible of various changes and modifications and that by the appended claims I intend to cover any such modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. An antenna unit adapted to be connected to a radio receiver of the all-wave type comprising an antenna system including a pair of conductors arranged in converging relation to form a nonuniform transmission line connected at its outer end to a pair of oppositely disposed doublet wires spaced apart a substantial distance in the direction of their lengths, said conductors being connected to a lead-in constituted by a pair of conductors arranged closely adjacent each other throughout their length, said transmission line being of suificient length to cause the surge impedance of said system to be gradually lowered from a relatively high value at the connection of said line to said doublet wires to a relatively low value at the connection of said line to said lead-in, means to couple said lead-in to said, radio receiver, and means connected to said coupling means whereby said antenna system is caused to operate as a doublet system over a high frequency band of radio signals and whereby said antenna system is caused to operate as a simple antenna over a low frequency band of radio signals.

2. In a radio apparatus of the all-wave type, a radio device having input terminals, an antenna of the doublet type for said device adapted to transfer signals with a reduced pick-up of local noise currents, a lead-in connected to said antenna comprising a pair of conductors arranged closely adjacent to each other throughout their length, a coil connected at two spaced points thereof to the lower ends respectively of said conductors, a capacitance means connected between an intermediate point of said coil and the grounded input terminal of said radio device, and means to connect one of said spaced points of said coil to the other, of said terminals, said 'at relatively high frequencies in operation of said apparatus the reactance of said capacitance means is so low that said intermediate point is effectively electrically connected to said grounded terminals and that at relatively low frequencies said reactance is so high that said intermediate point is efiectively electrically disconnected from said grounded terminal. I

3. An antenna system for a radio apparatus including two conductors in the outer portion of said system, said conductors being arranged in single doublet form and extending in substantially opposite directions, and means to connect said conductors to said radio apparatus and to cause the surge impedance of said antenna system to be substantially less in the portion thereof adjacent said apparatus than in said outer portion, said means including a gradually converging transmission line having a constant capacity and a gradually varying inductance per unit length,

the larger end of said line being connected to the inner extremities of said conductors and the other end of said line being connected through a lead-in to said apparatus.

4. An antenna comprising a pair of oppositely disposed conductors spaced apart in the direction of their lengths, and a non-uniform transmission line. including .a converging pair of conductors connected-respectively ,to the inner extremities of said first-named pair of conductors, the distance across the open end of said transmission line being of the order of magnitude of the distance between the apex of said converging pair and said open end.

5. An antenna for a radio apparatus comprising a pair of oppositely extending conductors spaced apart in the direction of their lengths, said conductors being connected to a gradually converging transmission line, said line having a constant capacity and a gradually varying inductance per unit length whereby the surge impedance of said transmission line diminishes as said line approaches said radio apparatus, the line bisecting the opening between said converging pair of conductors being vertical.

6. An antenna comprising a pair of oppositely disposed conductors spaced closely adjacent at their-inner ends and diverging from said inner ends to form a non-uniform transmission line, and a pair of oppositely disposed doublet wires connected to the open end of said line, the rate of said divergence being relatively rapid and the distance across the open end of the pair being of the same order of magnitude as the distance between said open end and said inner ends, whereby a transfer of radiant energy substantially equal to that in the direction of the line bisecting the opening between said pair of conductors oc curs in directions substantially perpendicular to the line of the oppositely disposed doublet wires.

7. In a radio receiver apparatus of the allwave type, receiver'input terminals, an antenna and a lead-inzconnected thereto comprising a pair of conductors arranged closely adjacent each other throughout at least a portion of their length, and means to couple said lead-in to said input terminals comprising a step-up autotransformer, said conductors being connected respectively to one extremity'of said autotransformer and a point intermediate said extremity and the other extremity of said autotransformer, one of said input terminals being connected to said other extremity, and circuit connecting and disconnecting means betweenthe other of said in 78 put terminals and a point of said autotransformer midway between said one extremity and said intermediate point to cause said antenna only to pick up radio signals over a predetermined wave band and to cause both said antenna and said lead-in to pick up radio signals over another predetermined wave band.

8. In combination, an antenna of the doublet type comprising oppositely extending conductors, the ends of said conductors nearer to each other being spaced apart a substantial distance, a pair of conductors, and conductors extending respectively from the opposite conductors of said pair to the inner ends of said oppositely extending conductors, said third-named conductors being spaced apart along their lengths by distances progressively increasing and such that the surge impedance of said third-named conductors at the ends thereof connected to said pair of conductors approximately matches that of said pair and the surge impedance of said third-named conductors at the ends thereof connected to said oppositely extending conductors aproximately matches that of said oppositely extending conductors.

9. In combination, an antenna system comprising an antenna of the doublet type including oppositely extending conductors spaced apart a substantial distance in the direction of their lengths, a pair of conductors, and conductors extending respectively from the opposite conductors of said pair to the inner ends of said oppositely extending conductors, said third-named conductors being spaced apart along their lengths by distances progressively increasing and such that the distance between half-wave resonance points on the reactance curve of said antenna system is substantially increased.

ROBERT B. DOME. 

